Arsenic is a ubiquitous environmental carcinogen that comes from both geochemical and anthropogenic sources. It has been linked to multiple health problems, including skin cancer, bladder cancer, diabetes, as well as cardiovascular and peripheral vascular diseases (1, 30). Consequently, the U.S. Environmental Protection Agency (EPA) ranks arsenic first its Superfund List of Hazardous Substances.
Inorganic arsenic, which is pervasive environmentally from geochemical origins such as volcanoes and hot springs can be either pentavalent (arsenate (As(V)) or trivalent (arsenite (As(III)). Biological activities includes incorporation of arsenic into organic molecules such as arsenobetaine, arsenosugars and arsenolipid, which are found in many marine organisms (8). Arsenic methylation also contributes to the arsenic biogeocycle (21). Microbial methylation, catalyzed by ArsM As(III) S-adenosylmethionine methyltransferases, detoxifies inorganic arsenic, producing a variety of less toxic species including MAs(V) (17, 18, 34, 35). In addition to biogenesis of methylated arsenicals, MAs(V) is also used as an herbicide. Approximately 3,000,000 pounds (1,360,000 kg) of MAs(V) are in commercial use in the USA. Its use has been banned by the EPA after Dec. 31, 2013 except for treatment of cotton because the EPA does not anticipate that arsenic in cotton will end up in the food supply (2). This may be an erroneous assumption since the herbicide can be degraded by microbial activity to MAs(III) and As(III), both of which are more toxic and carcinogenic than MAs(V) (36).
Aromatic arsenicals are also used in animal husbandry to prevent bacterial infections and for growth promotion. For example, derivatives of phenylarsonic acid (PAO) such as 3-nitro-4-hydroxybenzenearsonic acid (roxarsone), p-arsanilic acid, 4-nitrophenylarsonic acid and p-ureidophenylarsonic acid are all used as additives for animal feed. Roxarsone is degraded to 4-hydroxy-3-aminophenylarsonic acid (7) and eventually to inorganic arsenic (28). The related aromatic arsenical diphenylchloroarsine (Clark I) and related aromatic arsenicals were used as chemical warfare agents in World Wars I and II. After their use was abandoned, the compounds were often buried, where they were degraded to methylphenylarsinic acid (MPAA), dimethylphenylarsine oxide (DMPAO) and methyldiphenylarsine oxide (MDPAO), perhaps by microbial activity (3, 14).
Thus, a need exists for methods for detecting the presence of organic arsenic.